This research is directed towards specifying quantitatively the maximum safe dosage level of ultrasound in clinical work. The probable and possible hazards or toxic effects that may result from insonation of mammalian tissues and the mechanism of their production are being studied in a variety of organs in vivo. The dependence of the damage on ultrasonic field parameters and variables as well as on the tissue state are being evaluated in carefully controlled studies. BILIOGRAPHIC REFERENCES: Lele, P.P., Senapati, N. & Murphy, A.I. (1976), Studies on Acoustic Attenuation, Absorption and Scattering for Diagnosis of Tissue Pathology, Ultrasound in Medicine, 2, 523. Handler, R.A. & Lele, P.P. (1976), Intensity and State Dependence of Acoustical Absorption Coefficients in Mammalian Tissues, J. Acous. Soc. Amer. 59, S77.